Glassfiber Reinforced Gypsum (GRG) is a white ‘thin cast’ alpha gypsum that is field finished. Where once traditional ‘plaster castings’ were used, GRG is now specified because of its lightweight, superior strength and ease of installation.

GRG is the bridge to shapes and curves for the drywall/plasterboard trades. With the move away from "less is more" in the late 1970's and the re-introduction of traditional architectural forms, GRG evolved as the ideal medium. The construction boom of the past three decades established GRG as the means for architects and designers to achieve their design visions, while leveraging the experience of regular building trades.

GRG is a composition of high strength alpha gypsum reinforced with glassfibers that can be factory molded into any shape or size. GRG is a non-combustible material (test results of flame spread and smoke development values as per ASTM E-84-81a) and even the largest parts only weigh 2-3 lbs./sq. ft. (10-15 kg./sq.m.). Similar to traditional plaster castings but considerably lighter and stronger, GRG is typically field finished with any interior paint. Joints can be taped and finishing is similar to drywall finishing.

GRG is the most economical Formglas material and is used for columns, moldings, domes and ceiling elements.

GRG derives its strength from its form and is, therefore, ideal for shaped areas. Because of its thin shell, GRG behaves as a metal would in large flat areas and is prone to "oil canning". It is therefore not recommended for flat areas where drywall, for both aesthetic and economic reasons, would be a more appropriate application.


It is recommended that GRG products be installed by the drywall or carpentry trades in North America and the plasterboard trade elsewhere. The substrate should be of the same standard components as are used by these trades. Established criteria for control and expansion joints in drywall hold true for GRG.


GRG is typically field finished with an Alkyd primer and painted the same as drywall. Please contact Formglas to inquire about factory pre-finished GRG products. High gloss paints are not recommended because the hard GRG and softer tape joint compounds absorb paint and reflect light differently. Joint read-through will occur unless the taped surfaces blend smoothly and receive additional primer.

View GRG(Glassfiber Reinforced Gypsum) product specs here
In North America specify GRG under Section 9 — GRG is for INTERIOR APPLICATIONS ONLY